Metatropic Dysplasia I

Synonyms of Metatropic Dysplasia I

Chondrodystrophy, Hyperplastic Form

Dwarfism, Metatropic

Metatropic Dwarfism

Metatropic Dwarfism Syndrome

Metatropic Dysplasia

General Discussion

Metatropic Dysplasia I is a rare genetic disorder characterized by extremely small stature, with short arms and legs. Other characteristics of this disorder are a narrow thorax, short ribs, and kyphoscoliosis (backward and sideways curvature of the spinal column) which develops into short trunk dwarfism.

Signs & Symptoms

Metatropic Dysplasia I is characterized by abnormal skeletal development. Patients with this disorder typically have short ribs, short deformed arms and legs, kyphoscoliosis (abnormal curvature of the spine) and extremely short stature. A long narrow thorax, bulging joints with limited mobility of the knees and hips, and unusual increased extension of the finger joints are typical features.

An unusually long torso, which later develops into short trunk dwarfism due to curvature of the spine, is an early feature of Metatropic Dysplasia I. The spine develops a forward hump-like curvature causing a humpback.

X-rays show growth insufficiency of the vertebral column with flattening of vertebrae and often growth insufficiency in the arm and leg bones at the hip and shoulder joints. A crescent-like iliac causing a hump at the end of the spine is also apparent.

Causes

Metatropic Dysplasia I can be inherited as an autosomal dominant or autosomal recessive trait.

Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother.

In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed “dominating” the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.

In recessive disorders, the condition does not appear unless a person inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.

Affected Populations

Metatropic Dysplasia I is a very rare disorder that affects males and females in equal numbers.

Related Disorders

Symptoms of the following disorders can be similar to those of Metatropic Dysplasia I. Comparisons may be useful for a differential diagnosis:

Kniest Syndrome is a rare type of dwarfism that is characterized by unusually short arms and legs, a round face with hollow or depressed areas, swelling and stiffness of the joints, and a stiff drawing up (contractures) of the fingers. A cleft palate, curvature of the spine (scoliosis), vision and hearing problems may also occur. (For more information on this disorder, choose “Kniest” as your search term in the Rare Disease Database.)

Morquio Syndrome is a metabolic disorder characterized by an accumulation of keratan sulfate. Bony abnormalities of the head, chest, hands, knees, and spine may occur as a result of this defect. Intelligence is usually normal. The bony abnormalities of the spine can result in spinal cord compression. There also may be enlargement of the liver, curvature of the spine, a back flow of blood from the aortic valve of the heart into the left ventricle of the heart, as well as a loss of hearing. (For more information on this disorder, choose “Morquio” as your search term in the Rare Disease Database.)

Standard Therapies

Treatment of Metatropic Dysplasia I is symptomatic and supportive. When partial dislocation of the segments of the spinal column at the top of the spine (cervical vertebrae) is present, the joint between the two vertebrae can be fused together. This procedure should be done in order to prevent damage to the cervical part of the spinal cord.

Genetic counseling may be of benefit for patients and their families.

Investigational Therapies

Research on birth defects and their causes is ongoing. The National Institutes of Health (NIH) is sponsoring the Human Genome Project which is aimed at mapping every gene in the human body and learning why they sometimes malfunction. It is hoped that this new knowledge will lead to prevention and treatment of genetic disorders in the future.

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:

Years Published

1992, 1999, 2007

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